Electronic engine controllers are known in the art. Typically, such controllers are connected with various engine parameter sensors that produce engine parameter signals. Examples of typical engine parameter sensors include an engine speed sensor, an engine temperature sensor, a transmission speed sensor, a throttle position sensor, a brake position sensor, and a clutch position sensor, among others. The electronic controller inputs those sensor signals and produces a fuel delivery signal as a function of the values of those inputs. One prior art engine controller is the ADEM III controller produced by the assignee of the present patent.
Although prior art systems generally work satisfactorily, some have drawbacks. One such drawback is the microprocessor utilization required to sense engine speed, calculate an appropriate fuel delivery signal, and deliver the fuel delivery signal at the correct time. As is known to those skilled in the art, an engine speed sensor is typically used to sense the angular position of the engine, which in turn determines the appropriate time to issue a fuel delivery signal. Those engine speed sensors are typically proximity sensors associated with a rotating engine gear and have an output signal that varies as a function of gear teeth passing adjacent the sensor. Typically, an engine controller will produce an interrupt signal when each of the gear teeth pass the sensor. During that interrupt, the engine controller will typically calculate various values including: engine speed based on the elapsed time between adjacent engine gear teeth; fuel injection quantity; and fuel injection timing, among others. As will be appreciated by those skilled in the art, the microprocessor requires a certain amount of time to complete these calculations. As the engine speed increases, the number and rate of the interrupts will increase. There will be a maximum engine speed, above which the controller will be unable to perform the necessary calculations during the time period between passing teeth.
It would be preferable to have a system that could reduce the number of interrupts required to accurately control fuel delivery to the engine without causing engine performance or economy to suffer.